Matching different voltages??

[BiotechFusion]

I'm working on a simple alternator circuit but there's a few things I don't know. If I have a multi-phase alternator of 3 or more magnets rotating, I don't need a smoothing capacitor because the different phases add to make a smooth signal don't they? If I want it to be DC, do I still need a Wheatstone bridge even though its a smooth signal or just one diode? Some sources say a diode folds a wave form to make it all positive, but some sources say a diode only filters a wave form reducing the effectiveness of a waveform by completely dissipating the negative part of the wave form and reducing the actual energy that passes through while still preventing the current from being drawn in the other direction, which one is right? But, wait, if the magnets are oriented so that the South or North of each magnet is always facing outward...shouldn't that be DC by itself? But wait, the magnets would repel each other if the South end was always facing outward...but wouldn't that not be a problem in a symmetric alternator as long as the magnets are held in place well enough?

 

Or, it's smooth, but would the alternator still draw current as much as at gives current even though all the different phases should add together?

What kind of component do I use to transform a variety of voltages on one end into a single voltage on the other end of the component? Do variable transformers exist?

 

Another thing I can't figure out is what if I don't want the circuit to draw electricity when it's not giving something power? Would only a single diode be needed to do that?

[John Cuthber]

It's difficult to tell what you are asking.

Are you looking for this sort of thing?

http://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/rectifier-circuits/

[studiot]

AC is AC and DC is DC.

 

You will never obtain pure DC from an AC supply without an energy storage element in the rectification circuit.

You would need an infinite number of phases to do this.

This element is usually a capacitor.

 

The output from any number of rectifying diodes is fluctuating DC, called ripple.

This fluctuates above and below the desired output voltage.

The energy storage element supplies the desired output when the rectifier output is below.

 

Note below does not mean negative, just less than.

 

Yes you can convert multiphase to single phase via a suitable transformer.

[BiotechFusion]

AC is AC and DC is DC.

 

You will never obtain pure DC from an AC supply without an energy storage element in the rectification circuit.

You would need an infinite number of phases to do this.

So in other words, if I had like 8 phases and one diode, it would approximate a smooth DC current but still have a few small but negligible lumps? Keep in mind this is not the typical alternator design that you'd see in something like a lawn mower, rather just a single cylindrical but very tight coil of copper containing a rotor with several magnets on its surface inside, there is not necessarily a N and S of the magnet with equal effectiveness which is also what I am asking about. I am distinctly NOT doing this

but am instead doing this

with this distinction that the copper is wound like below this due to limited or unnecessary production capacities that inhibit such fine detailed winding. And also, is it a problem if I have all the magnets in the rotor facing outward in the same manner with the same orientation? With this kind of copper coil, the magnetic field should always (approximately) be perpendicular to the copper coil and maximize the effectiveness of the magnetic field, since only a perfect circle would be perpendicular to an (approximately) radial magnetic field along the length of the magnet at every point (approximately), and the cylinder almost forms perfect circles when tightly wound. Why not just have all the magnets be S and S and S and S facing outward if I have an external source turning the alternator? Wouldn't it still just be a magnetic force pushing on charges over a distance to create energy? I could see how in the case of the first design, I would need a N and a S to actually make the wire turn, but I'm not trying to make the wire turn, I just have an external source making the rotor turn and I just want electricity to flow through a stationary wire kind of like a wind turbine or hydroelectric generator, or actually maybe almost exactly like a wind turbine but smaller. Wait...is what I'm trying to do a generator and not an alternator? If it's a generator and everything I said was true about the wire being stationary and approximating parallel circles perpendicular to the magnetic field lines and having the magnets all be S S S, that would make it a smooth DC current on its own right??

 

 

 

Yes you can convert multiphase to single phase via a suitable transformer.

Ok, but I don't really mean multi-phase at one voltage, I mean a fixed number of phases but with the alternator rotating at various frequencies and thus creating different voltages. Maybe a capacity would be in handy here? Or is there a type of transformer that can just convert a lot of different voltages almost at once and turn it into one single voltage?

Edited April 24, 2016 by BiotechFusion

[studiot]

 

but with the alternator rotating at various frequencies and thus different voltages.

 

That is why cars have regulators and cutouts.

They also have huge capacitors called automotive batteries.

 

if I had like 8 phases and one diode, it would approximate a smooth DC current but still have a few small but negligible lumps

 

 

The ripple waveform is nothing like your picture. It is often a form of sawtooth.

The current waveform is even more different and occurs as a series of short term pulses of very high current (do you understand why this must be so?)

 

The 'bumps' may or may not be negligible, you would have to calculate that and you should be looking at the bumps in the current waveform more than the voltage.

 

Polyphase generators are produced to reduce the height of the current pulse and the depth of the ripple sawtooth, becuase they reduce the time between current pulses.

Google polyphase generators for lots of waveforms and specifications.

[BiotechFusion]

 

That is why cars have regulators and cutouts.

They also have huge capacitors called automotive batteries.

 

 

The ripple waveform is nothing like your picture. It is often a form of sawtooth.

The current waveform is even more different and occurs as a series of short term pulses of very high current (do you understand why this must be so?)

 

The 'bumps' may or may not be negligible, you would have to calculate that and you should be looking at the bumps in the current waveform more than the voltage.

 

Polyphase generators are produced to reduce the height of the current pulse and the depth of the ripple sawtooth, becuase they reduce the time between current pulses.

Google polyphase generators for lots of waveforms and specifications.

Yeah I think polyphase is the idea I had, because I didn't want the generator to blow up the rest of the devices and I solved that by using smaller magnets and I also wanted the phases to add together to make something resembling a smooth waveform.

 

But see in the case of something like this

https://qph.is.quoracdn.net/main-qimg-5edbe0cc97c4f4c9b688282547d998b0?convert_to_webp=true

Now, just imagine that but with the simple cylindrical copper coil structure I had instead of those 8 different mini coils and that's what I'm trying to do. Also how would you even connect those 8 different smaller coils into a circuit?

why do I need a N N N N and S S S S halves? Why not just have all the magnets be N N N N N N N N or all be S S S S S S S S facing to begin with and avoid that lower half and just make it positive? It's just magnetic force pushing charges over a distance and I'm not trying to make a motor to turn something like a lawn mower blade, I just don't understand why people bother with S AND N in this case. If I arrange the bar magnets running along the length of the rotor so that for each magnet, only the S is facing outward and almost touching the copper coil, and the N side is always facing inwards, away from the copper coil, why is that a problem? As long as they're welded or glued well enough the repulsion shouldn't make them fly apart.

Edited April 24, 2016 by BiotechFusion

[studiot]

 

Why not just have all the magnets be N N N N N N N N or all be S S S S S S S S

 

Because magnetic monopoles have never been observed, even though they have been posited to exist.

 

Modern permanent magnets certainly have much greater magnetic density than older materials.

 

You haven't answered my question about current.

[BiotechFusion]

 

Because magnetic monopoles have never been observed, even though they have been posited to exist.

It's a good thing I'm not talking about monopoles then or that would be a huge problem. All I'm saying is, if you have a rectangular magnet with N going out one side and S going out the other, have the S all pointing outward towards the copper coil and have the N all pointing inward towards the center of mass of the rotor. That way you only get DC because the S part of the magnetic field will certainly be stronger as it is closer to the coil and you won't have that switch between N and S which each turn of the rotor.

 

 

You haven't answered my question about current.

I don't know if it's actually relevant anymore because if I start with DC, I don't need to convert from AC to DC, hence my question about if what I'm trying to make is actually a generator, not an alternator.

 

But on the other hand, generators should also draw current when they aren't being used...shouldn't they? So can I just use a diode to prevent a generator from drawing current? Or is that only for alternators once again?

Edited April 24, 2016 by BiotechFusion

[studiot]

 

So can I just use a diode to prevent a generator from drawing current? Or is that only for alternators once again?

 

 

Yes a diode will prevent reverse current flowing. That is its function. Diodes used for protection like this are common.

If the current draw is significant the ohmic heating effect in the diode can be significant as well.

 

Generator is a generic term for dynamos (DC) and alternators (AC).

Dynamos are significantly larger and heavier than alternators for the same current or power generation, because the alignment with the generating coil is only optimum for a short time.

(This is actually almost the same effect as the question I asked you about ripple current and you declined to answer.)

[BiotechFusion]

 

Yes a diode will prevent reverse current flowing. That is its function. Diodes used for protection like this are common.

If the current draw is significant the ohmic heating effect in the diode can be significant as well.

 

Generator is a generic term for dynamos (DC) and alternators (AC).

Dynamos are significantly larger and heavier than alternators for the same current or power generation, because the alignment with the generating coil is only optimum for a short time.

(This is actually almost the same effect as the question I asked you about ripple current and you declined to answer.)

Ok, well thanks for answering the diode problem. So now, what is this thing I'm trying to make generating? It should be making DC, and it might be bulkier than a thin little wire between a few magnets. Does a dynamo generate less power because the N end of the magnetic field is still somewhat close to the outward facing S end even if the S end is closer, thus lowering the net magnetic field experienced by the coil? But..wait...again I'm not trying to make a motor, so even in the first design I presented with the thin wire between a N facing magnet and a S facing magnet...why not just have two N facing magnets if there's an external source turning the wire?

[studiot]

 

why not just have two N facing magnets if there's an external source turning the wire?

 

 

Look at the first picture in your post4 and plot the magentic field lines for 0^o and 90^o

 

How many lines of magnetic force thread the loop at each position?

[BiotechFusion]

 

 

Look at the first picture in your post4 and plot the magentic field lines for 0^o and 90^o

 

How many lines of magnetic force thread the loop at each position?

Don't know, the magnetic field lines are proportional to the strength of the magnetic field which is proportional to the current. I'm not given resistance so I can't use Ohm's law to find the current.

But, again, if I just have two South facing magnets, wouldn't the sine wave just have positive pulses instead that negative half waveform that goes to the negative value? Why not?

I think this is what I'm trying to make, https://en.wikipedia.org/wiki/Permanent_magnet_synchronous_generator

I'm using permanent magnets to push charges in stationary coil, and since the magnets are attached to the coil, the magnetic field rotates at the same speed as the magnets. So why not just have all the magnets attached to the rotor all be facing S outward and get a smooth DC current with a 3 or 4 phase generator?

Btw a moving magnetic field would create an electrical field wouldn't it? Is that why the magnetic field moves charges as if they were in an electric field?

Edited April 24, 2016 by BiotechFusion

[studiot]

 

I think this is what I'm trying to make, https://en.wikipedia...onous_generator

 

But that is an AC machine.

 

make you mind up do you want a dynamo or an alternator?

Edited April 24, 2016 by studiot

[BiotechFusion]

 

But that is an AC machine.

 

make you mind up do you want a dynamo or an alternator?

I don't know what you've been reading exactly but that's the exact question I've been asking you this whole time, what will this device end up being? Ideally I'd want DC right off the bat but every time I ask you a question to determine how/if I can do that in the manner i describe I don't see a clear answer. It appears even a permanent generator isn't an exact match for what I'm looking to make, they still have alternating N and S magnets instead of all S.

 

Just imagine this

but with a single cylindrical coil parallel to the surface of the rotor instead of 8-12 perpendicular coils and two or more S outward-facing magnets instead of a single or alternating N and S magnet(s). Will that be DC or AC? And why or why not? How can it be rectified if AC, keeping in mind one end of the copper coil will have to loop all the way back around the stator to complete the circuit?

 

In fact, mathematically, let's say I could cut up a flat bar magnet into an infinitely thin slice that maintained its magnetic properties. If I aligned an infinite number of those magnets in such a way that (even though they would try to repel each other) all the S ends were touching and all the N ends were touching, but, that the S ends were facing outward and the N were facing inward, I would have a continuous S part of the magnetic field surrounding the outside of the stator as the S end would be passing through the coil with the most strength due to the shorter distance from the S end to the coil, a sort of infinite-phase generator with no negative sinusoidal component, no N, thus I should have only DC current. All I'm waiting for you to do is confirm yes or explain why not. So far I've had one real life physicist say "yes that would be a smooth DC current" even if it would be weaker due to the fact that some of the strength of the S end would be masked by some of the N end that still radiated outward, but I don't know they aren't in expert an electronics.

Edited April 25, 2016 by BiotechFusion

[John Cuthber]

"I don't know what you've been reading exactly but that's the exact question I've been asking you this whole time,"

Why didn't you say so?

[BiotechFusion]

"I don't know what you've been reading exactly but that's the exact question I've been asking you this whole time,"

Why didn't you say so?

I thought I did with questions like "So now, what is this thing I'm trying to make generating? It should be making DC..." and "So in other words, if I had like 8 phases and one diode, it would approximate a smooth DC current but still have a few small but negligible lumps?" and "if the magnets are oriented so that the South or North of each magnet is always facing outward...shouldn't that be DC by itself?" and "Will that be DC or AC?," Like more than half the stuff I'm talking about is if whether it will be DC or if I need to rectify it. If this model I'm trying to make is DC, then a majority of the thread is resolved, it would mainly be the transformer problem that is left.

So, to go over it, I'm using a single, cylindrical copper coil as a stator that is parallel to the length of the rotor. The coil approximates circles when tightly wound. The magnetic field is radiating outward from the surface of three magnets on the rotor. The magnets on the rotor are all S on the outside, pointing N on the inside so that only the S end of the magnet is in the proximity of the coil on each magnet. In effect, there will be less surface area than typical generators for the copper wire, but, the poles of the magnets are pointing towards the coil. The magnetic field the coil experiences should be stronger just as the magnetic field at the poles of the Earth is stronger, and, what I think is it should always be DC since only the S end of each pole is close the coil at all times in the cycle. Is this true or not?

 

And, if had just a typical rotor with alternating N and S magnets instead of only weaker S, what is the typical pattern for rectifying 2n number of magnets? Sometimes I see diamond shaped wheat-stone bridges, sometimes I see grid-like layouts with 6 diodes. Why can't I just use one diode to prevent the current from being drawn and rectify it? How would this kind of model be rectified?

Edited April 25, 2016 by BiotechFusion

[studiot]

You originally stated you were constructing an alternator.

You also stated that you don't need a capacitor to output DC from this generator.

 

Subsequent discussion shows that you do not understand the basics of rectification or stabilisation.

 

You also made various statements about the construction of the 'alternator' or whatever which demonstrate that you do not understand the electromagnetics of generators either.

 

Yet when asked two key questions about stabilisation and electromagnetics your replies were flippant.

 

The magnetic path inside a generator is quite tortuous and you need to understand both it and the right hand rule to understand why spinning a few magnets on axis inside a coil will not get you much electricity.

 

You also need to understand that conventional electricty only flows from positive to something less positive.

 

There is a very old fashioned and inefficient type of DC generator that is similar to what you are proposing, using what was known as a ring wound armature.

 

https://www.google.co.uk/search?hl=en-GB&source=hp&biw=&bih=&q=ring+wound+armature.&gbv=2&oq=ring+wound+armature.&gs_l=heirloom-hp.3..0i22i30.1437.1437.0.2265.1.1.0.0.0.0.125.125.0j1.1.0....0...1ac.1.34.heirloom-hp..0.1.125.UuANibjDcKU

[BiotechFusion]

You originally stated you were constructing an alternator.

Which may or may not still be the case, I don't know, that's why I'm asking.

 

You also stated that you don't need a capacitor to output DC from this generator.

 

I *asked* if I didn't.

 

Subsequent discussion shows that you do not understand the basics of rectification or stabilisation.

Never said I did, I don't do much with electronics.

 

 

You also made various statements about the construction of the 'alternator' or whatever which demonstrate that you do not understand the electromagnetics of generators either.

Which, again, is why I'm here asking questions, questions that you refuse to answer or simply don't know the answer to.

 

Yet when asked two key questions about stabilisation and electromagnetics your replies were flippant.

I asked perfectly reasonable questions, it's your toxic attitude that's flippant, you've done nothing to help this discussion.

 

You also need to understand that conventional electricty only flows from positive to something less positive.

Their direction of +/- depends on the circumstance and materials. In reality it is possible to move both positive and negative charges.

 

 

https://www.google.co.uk/search?hl=en-GB&source=hp&biw=&bih=&q=ring+wound+armature.&gbv=2&oq=ring+wound+armature.&gs_l=heirloom-hp.3..0i22i30.1437.1437.0.2265.1.1.0.0.0.0.125.125.0j1.1.0....0...1ac.1.34.heirloom-hp..0.1.125.UuANibjDcKU

I guess that remotely resembles what I'm talking about, but not close enough to be useful. I suppose I should just stick with real physicists at my university for questions, though I certainly don't want to assume everyone here is as negative as you.

Edited April 25, 2016 by BiotechFusion

[Phi for All]

Which may or may not still be the case, I don't know, that's why I'm asking.

 

I *asked* if I didn't.

 

Which, again, is why I'm here asking questions, questions that you refuse to answer or simply don't know the answer to.

 

I asked perfectly reasonable questions, it's your toxic attitude that's flippant, you've done nothing to help this discussion.

 

!

Moderator Note

Making a statement followed by a "don't they" or "isn't it" type of query is a funneled question. With this approach, you aren't asking a question about the science, you're asking if the respondent agrees with you (and they may agree with parts but not all of it). You've funneled the question so yours is the only answer. It makes it appear you're assuming you're right, and inviting others to agree or disagree.

 

This is probably why you're getting some pushback. Let's all take a breath before continuing.

[BiotechFusion]

 

!

Moderator Note

Making a statement followed by a "don't they" or "isn't it" type of query is a funneled question. With this approach, you aren't asking a question about the science, you're asking if the respondent agrees with you (and they may agree with parts but not all of it). You've funneled the question so yours is the only answer. It makes it appear you're assuming you're right, and inviting others to agree or disagree.

 

This is probably why you're getting some pushback. Let's all take a breath before continuing.

That logic doesn't follow, I'm not assuming I'm right, I want to know if a particular conjecture is right, I'm just the one who happened to make said conjecture.

[John Cuthber]

If you really want DC generator then this might be the least bad option.

https://en.wikipedia.org/wiki/Homopolar_generator

they pretty much suck, but they are useful in a few instances.

 

What are you actually seeking to achieve?

[BiotechFusion]

If you really want DC generator then this might be the least bad option.

https://en.wikipedia.org/wiki/Homopolar_generator

they pretty much suck, but they are useful in a few instances.

 

What are you actually seeking to achieve?

I mean I appreciate the suggestion but I don't understand why you gave me some other model instead of just telling me if my current model will work. I'm just trying to see if I can make something generate DC current when I don't have the option to make 100000000000 coils at a micron level. Basically, I'm building a basic generator from scratch. Although, something else that may be relevant...do you happen to know if there's some kind of material that can increase the inductance of the coil or the effectiveness of the magnetic field?

Edited April 25, 2016 by BiotechFusion

[John Cuthber]

It is far from clear what your "current model" is.

 

" Basically, I'm building a basic generator from scratch."

have fun, but if you want something that works well either buy one (which I accept is no fun at all) or find a good book on motor design.

"Although, something else that may be reverent...do you happen to know if there's some kind of materiel that can increase the inductance of the coil"

Yes, that's why most motors transformers and generators etc have "iron" cores with winding round them. That's what the iron is for.

 

(and it's more likely to be relevant than reverent)

Edited April 25, 2016 by John Cuthber

[BiotechFusion]

It is far from clear what your "current model" is.

I described it in detail several times, you'll just have to read it.

[Enthalpy]

Some general remarks.

 

BiotechFusion, if you want to learn some electromagnetics and electric machinery, go on. If instead you want something that works properly within a limited time, buy it. Generators are cheap, often you find some used ones for free, you'll save months of disappointment, because EM isn't trivial and takes its time to grasp. Presently you're many months away from building a usable generator.

 

You could acquire "Electric machinery fundamentals" by Stephen Chapman. Not more complicated than it needs, nice pictures, but it's the level of engineering students. Or accept a less numerical but much more "hands on" understanding - which has as much value to my eyes, and in my opinion should be acquired before the numerical approach - and buy yourself an experiment kit for electromagnetism.

 

The universal and justified choice is to build (AC) alternators and, if DC is desired, put diodes. Diodes are very cheap and reliable - much more so than the additional parts in a (DC) dynamo. Nobody would have a single diode: buy a bridge, it makes use of all alternances. 4-diode bridges for single-phase AC to (rippled) DC, 6-diode bridge for three-phase AC to (rippled) DC. Same size and price as a single diode.